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Community metabolism and nutrient cycling in the Mississippi River plume: evidence for intense nitrification at intermediate salinities
Pakulski, J.D.; Benner, R.; Amon, R.; Eadie, B.; Whitledge, T. (1995). Community metabolism and nutrient cycling in the Mississippi River plume: evidence for intense nitrification at intermediate salinities. Mar. Ecol. Prog. Ser. 117(1-3): 207-218
In: Marine Ecology Progress Series. Inter-Research: Oldendorf/Luhe. ISSN 0171-8630, more
Peer reviewed article  

Available in Authors 

Keywords
    Abundance; Biological production; Dissolved inorganic matter; Hypoxia; Nitrates; Nitrification; Nitrites; Nitrogen; Nutrient cycles; Oxygen consumption; Respiration; River plumes; Salinity; Bacteria [WoRMS]; Marine

Authors  Top 
  • Pakulski, J.D.
  • Benner, R.
  • Amon, R.
  • Eadie, B.
  • Whitledge, T.

Abstract
    Community respiration, net nutrient fluxes and heterotrophic bacterial production were investigated in the Mississippi River (USA) plume during May 1992 using dark bottle incubations of unfiltered water. Highest rates of community O2 consumption and dissolved inorganic carbon regeneration were observed at intermediate (10 to 27 ppt) plume salinities. Plume surface O2 consumption rates were 2- to 4-fold greater than rates reported previously during the summer and winter. Heterotrophic bacterial production ([3H]-leucine incorporation) was also highest at intermediate salinities and 2 to 4-fold greater than rates reported from other seasons. Net regeneration of NH4+ was observed in the 0 to 18 ppt region of the plume while low rates of net NH4+ consumption were observed at 27 ppt. Net NO2- regeneration in the Mississippi River suggested the occurrence of nitrification in the fresh waters of the delta. Serendipitous observations of rapid NO3- regeneration at 18 and 27 ppt indicated the development of intense nitrification at intermediate plume salinities. Nitrification accounted for 20 to > 50% of the community O2 demand at 18 and 27 ppt. These data indicated that nitrification was an important component of the plume nitrogen cycle and contributed significantly to oxygen consumption in the plume.

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